Engine valve-gear.



c. E PEEs'ooTT. ENGINE VALVE GEAE. A-PIKLIQATKION FILED JULY 16. 1907-l 9. 0 9 1 2,. l m ME m a D...

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C. F. PRESGOTT.

ENGINE VALVE GEAR. APPLIUATIQN FILED 1111116. 1907.

- Patented Jan. 12,1909.

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'www0/awo G. F. YRBSGOTT.

ENGINE VALVE GEAR.

A PPLIOATION FILED JULY 16, 1907.A y

Patented Jan. 12. 1,909.

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PHILADELPHIA, PENNSYLVANIA.

ENGINE VALVE-GEAR.

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Specification of Letters Patentn Patented Jan. 12, Li909.

Application ledJuly 16, 1907. Seriall No. 384,054.

act positively to'decrease the linear' advance' of an auxiliary exhaust or compression controlling valve relative to the linear advance of the valve which admits and cuts off the steam, or in other words, t-o accelerate the linear advanceof the valve that Icuts off the l steam, relative to the linear advance of the exhaust valve, thus so timing the operation of the valves as to delay the point-s of exhaust opening and exhaust closure. This holds the steam Within the cylinder during the greater portion of each stroke, thereb Y increasing the ratioof expansion, decreasing the terminal pressure and getting more Work from a given quantity of steam. By delaying the closing of the exhaust port at all points of cut ofi. the volume of steam in compression is decreased, and this decreases back pressure. hereafter in the specification that the phrases to delay the exhaust closing relative to the Inain valve or to accelerate the main valve relative to the exhaust are used indiscrimi? mately, and are to he understood as practr cally synonymous for the results obtained are precisely the same.

Another object of my invention is to provide a'compression controlling valve which will open for exhaust vsimultaneously with or later than the main valve, but so arranged as to closefor compression much'later than the main valve.

My invention consists broadly in the provision of an auxiliary exhaust or compression controlling valve and positively actuated mechanism for operating it, so arranged and connected to the auxiliary valve and to the steam inlet valve that the auxiliary valve is always moving behind the steam .admission and cut off valves, and with a decrease in its `linear advance relative thereto. It also consists in a motion foroperating these valves dina'ry rived from the cross head of the engine, this of an engine,

It is therefore to he understood that.

compounded of a from a reciprocating rocking arm of an crtypc, and a secondary motion ldesecondary motion acting to delay and modify the movement of the'valves due to the rocking arm.v

primary mot-ion y derived l In the draWings,' F-igure l is a side view partly broken away of a simple form of engine cylinder and connected mechanism. F ig. 2, is a vertical section ythereof on line 1-1 of Fig. l. Fig. 3, is a plan view there# of in section on lines 3- 3 of Figs. 1 and 2. Fig. el, is a diagram showing the movements of the auxiliary valve and steam valves relative to the movement of the piston at various points of the piston movement With'the construction shoivn in Fig. l. Fig. 5, is a simi..-

-lar diagram vshowing the effect of a modified Fig, 6, is a view in form of valve motion. end elevation of Fig. 1.

Throughout the several vieWslike parts are indicated by like reference characters.

In the drawings l designates the cylinder 2 and 2 the heads thereof, .and 3 a valve chest thereon having a steam space in the center thereof, and the exhaust spaces 3, 3.at both ends.

Ll, 5 and 6 designate ordinary piston valves `for admitting and cutting oli' steam and opening the exhaust ports, 4L and 6 being the steam admission and cut oli' valves, ande the auxiliary exhaust valve. This last valve has a 'shorter lap than the Valves l and 6, and might indeed be made solid from one end to the other as far as its operation as a co1npression regulating valve is concerned. It is not shown solid however, and would of course not be solid in practical use. All the valves as I have shown them have the valve heads 'connected by' reduced interme diate portions. valves for the purpose of illustration and because of their simplicity, it will he understood that I donot Wish to confine myself to this form inasmuch the ordinary slide valves would operate in precisely the same Wa 'lrhe valve chest is provided' with the ports 7,7. having passages leading directly into the cylinder at the extremities thereof. These ports are adapted to be covered or uncovered in the usual mannerby the heads of the valves as the valves are reciprocated. The valve heads on valves 4 and 6 act 'to connect the ports alternately with thesteam While I have shown piston A valves 4 and 6 and hence the need of the diiierential valve movements now to be described. This valve movement is conipounded of a primary movement derived from`a rocking shaft in the usual manner and a secondary movement derived from the cross head of the engine.

In detail 8 and 11 designate two parallel rocking arms actuated by a Stevenson link motion as shown in Fig. 1, and said arms 8 and-11V are connected by a link 9. In line withv arm 11 and laterally disposed with relation thereto is a corresponding rocking arm 11 both of said arms 11 and 11 being mounted on a rod 11b forming the axis of the movement of said arms. Rotatably supported or otherwise mounted on the extremities of these arms 11 and 11 is a transverse shaft or pintle 10. y

The Stevenson link motion shown in Fig. 1 comprises the usual eccentrics 8a Vturned by the drive shaft of the engine 8e, Vo erat ing to reciprocate links 8b, the latter eing connected to the opposite ends of a slotted link 8c. TheV block 8d to which the lower ends of arms'8 and link 9 are connected is mounted in the slotin said link8C. -By raising and lowering this link 8c, the engine can be reversed, as is well known inthe art.

As shown in Fig. 8 the arm 1l extends Somewhat beyond the shaft 10 and at its extremity is pivotally connected by a link 18 with the rod 18 of the auxiliary valve 5. Pivotedto 'the extremity of the arm 11 on theaxial line 5 of the valve connection 1S is a link '17, which extends downward and is in turn pivoted to a link 16 which at its forward end ispivotally attached to a fixed arm 15 projecting from the cross head 14 of the engine. Connected to link 17 below its pivotal connection with the link 18 is the valve rod of the usual steam valve 4. `Preferably I use twooi' these steam inlet and cut olf valves 4 and 6, their rods 19 and 20' being connected by links 19 and 20 to a pintle or shaft 21 which is mounted on link 17 below the upper pivotal point of the link as shown clearly in Fig. 8.

As shown inFigs. 1 and 3,'the valve 5 including its heads is not. as long as the valves 4 and 6, and hence when the ports of valves 4 and 6 at the right hand end of the cylinder are open to steam pressure as seen in Fig. 1, the like port of valve 5 is closed, the valve being edge to edge with the portl while at the opposite end of the cylinder at this time when the spent steam is exhausting, the valve l5 does 'not close the port, but is in line with the valves 4 and 6. It will also be obvious that the compound motion derived from the rocking arm 11 and the cross head 14 will act to accelerate the movement of valves 4 and 6 relative to the valve 5, or in other words act to delay the linear advance of the valve 5 relative to the valves 4 and 6 in every position of the valves, and that this will thus secure a delay in the events of the exhaust opening and closure.

From the position shown in Fig. 1 the action of the valves'is as follows: In this position the inductionvalves 4 and 6 are open to the extent of the steam lead, the exhaust vvalve 5 however having less length of movement by reason ot' being pivoted to the ot' the link 17 is not moved past the port 7 and thereforecloses the same. In this position the cross head is aboutto move toward the crank, and the rocking arms have not yet quite completed their movement toward the cylinder. As a consequence the valves 4 and 6 will open to the tall extent, (the valve 5 opening slightly to steam if desired'). As the cross head moves forward it swings the link 17 'forward also upon its pivotal axis 5, thus modifying the rearward moement of ther rocker arms 11 and 11, as otherwise communicated to the valves 4 and 6, and tending to carry these valves towards the crank end of the cylinder. `Now upon this move-ment, thevalves 4 and 6 act at the proper time to close the port 7 and cutv oit the steam to the cylinder. By reason `of their relative swt'tness and movement due to the point of connection to the link 17, valves 4 and (i pass the valve 5 and move through the remainder of the stroke in kadvance ot it, and in due course open the exhaust. ports behind them. The heads-4', 6 then cut ott the exhaust ports 7 and. if there were no auxiliary 'valve the'fsteam in the crank end et the cylinder Ywould be under compression for the remainder of the stroke; compression would occur as usual and the terminal pressure be relatively great with a consequent loss of power. As it is the auxil iary compression valve being delayed, the middle exhaust port remains open until nearly the end of the stroke and the valve 5 only closes the auxiliary exhaust port just before the piston reaches the end ot the cylinder.

The ottiti'eoi ithe auxiliary valve is first to delay Vthermal closure of the exhaust port until the piston has completed about 90% of its stroke, thus preventing undue compression, and second to provide additionalarea of exhaust port opening so as to reduce back pressure.

The final closure of theexhaust port 'is fixed by the auxiliary compression controlling valve and is delayed until the piston has completed about 90% of its stroke, thereby decreasing the volume of steam in compression.

' The relative motion of theseveral` valves,

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connected as shown in Figs. 1 and 3 andhefore described, is shown in the diaoram Fig. 4. There l1b designates the axis of the rocking arm 11, 18 the of the valve rod 18', Q0 the point of connection of the valve rods 19', 20', and /z the line of movement of the cross head.

At the time of admittin et and 6 are behind the va of eut loil the valves et. and (Shave -moved more nearly in the line with the valve at the middle position the valves ai'e practically in line; at the point of release the valves 4 and 6 are in advance of the valve 5,

and this advance is maintained from the point of release to the closing of the exhaust and the admission of steam.

. While l have described one method of securing the result which I desire, 'it will he seen from Fig. 5 thatthe same result will' be attained if the link 17 is carried upward beyond its pivotal point 5 and the valve 5 be connected to the extended upper end of the link 17. Su'ch a combination of parts is shown in the diagram Fig. 5, wherein the letters are the same as in the diagram Fig. 4. rllhus from the motion of the rocker 11 towards the cylinder and the crankward move` mentv of. the cross head, the valve 5 will lie moved towards the right the steam valves will be moved towards the crank end of the cylinder and will pass the auxiliary valve, continuously traveling in advance of said valves and that thus the same effects will be attained as with the arrangement shown in Fi .6.

s before stated in the beginning of the specification, my sole object is to provide apositive means for operating an, auxiliary exhaust or compression controlling valve. I am aware that auxiliary compression con# trolling valves have heretofore been devised,

but such valveshave heretofore not had 'positive operation and act therefore difterently at different speeds ofthe engine. Such valves also have been incapableI of regulation to suit changes in the speed.

My invention provides avery simple and effective lconstruction composed of elements 4which are well known in engine designing, and with. which locomotive en ineers are fully acquainted. It can be regu ated to suit the exigencies of any particular case, and it is entirely positivein its action.

ln addition it may be pointed out that my valve gear avoids the use of a multiplicity of parts or the use .of springs, counterweights, ,toothed gears, dash-pots or other devices -of like-character which havebeen employed in the attemptto obtain like results. A

While I have shown piston valves, dfiv not wish to be limited to this form, nor do l wish to be limited to the use of threef valves,

oint of connection.

steam, the valves ve 5; at the 'point Having thus described my invention what l claim as new and desire to secure by Letters Patent is:

l. ln valve gears for steam engines, a cylinder, a steam chest, admission and eX- haust ports connecting thesteam chest with the cylinder, auxiliary exhaust ports, a main .valve controlling the admission and exhaust through said steam ports, a compression regulating valve controlling thc-auxiliary exhaust ports, and mechanism operated by the engine tor movingr the main valve at an accelerated speed and linear advance relative to the speed and linear advance or the auxiliary valve.

2. ln valve gears for steanrengines, a cylinder, a steam chest. admission and linusi ports connectinv the steam chest with the cylinder, auxiliary exhaust ports, a main valve controlling the admission and exhaust through the said steam ports, a compression regulating valve controlling theyauxiliaiy poi'ts,'a primary valve motion, a secondary valve motion having a lead over said primary valve motion, a link connecting said primary ivithsaid secondary' motion, and means for connecting said auxiliary valve and said main valve 'to said link in such manner that the linear advance of said main valve shall ybe accelerated relative to` the linear advance of said auxiliary valve at all points of eut olli. Y

ln valve gears t'or steam engines, a

cylinder, a steam chest. admission and exhaust ports connecting the steam chest with the cylinder, auxiliary exhaust ports,'a. main valve controlling the admission and exhaust through the steam ports, a compression regulating valve controlling A'the auxiliary exhaust ports, a primary rocker arm, means for operating the arm fromm moving part of the engine, a secondary reciprocating element, a link connecting the two and modiloo tied in its movement by therelative motions 1 of said primary and secondary motions, and auxiliary valves connected at such points on Vsaid rocker arm that the linear 'advance of the main valve shall be accelerated relative tothe'linear advance ot said auxiliary valve. Li. ln valve gears for steam engines, a

cylinder, a cross head connected to the piston, a steam chest, admission and exhaust ports connecting the -steam chest to the cylinder, .auxiliary exhaust ports, a main valve controlling theadmission and exhaust through. the steam ports, an auxiliary compression regulating Valve controlling the auxiliary exhaust ports, a rocker arm, means for operating the arm from a moving part of the' engine, a4 link pivot-ed to the extremity 'of said rocker arm at one end and .connected with said, cross head at the other end, and a valve rod connecting said auxiliary valve to said vlink at its pointof connection with the rockerarm.

Y 5. In an engine valve gear, the combination with a cylinder', a steam chest, admission and exhaust ports connectlng the steam chest with the cylinder, auxiliary exhaust. `ports and main valves controlling the admission and exhaust through the steam ports, a compression regulating valve conan oscillating auxiliary link pivoted to the Vextremity of said last named rocking arm and pivotally connected to the cross-head of the engine, a rod connected to the auxiliary valve and to the said rocker arm, and a valve rod pivoted to said link below its pivotal connection vvith said rocker arm and below the pivotal connection of the auxiliary valve rod.

6. In valve gears for engines, a cylinder, a steam chest, a plurality of valve chambers communicating with the steam chest, admission and exhaust ports connecting each valve chamber with 4the cylinder, an auxiliary valve chamber having exhaust ports leading from the cylinder, main valves controlling the admission and exhaust of steam located in the said valve chambers, a compression regulating valve controlling the auxiliary exhaust ports therein, a piston in said cylinder, a rocking arm means for operating the arm from a movable part of the engine, a cross-head attached to said piston, means for operating said .cross-head in lead 'of said 4eoaeers rocking arm, a rocking arm parallel to said first named rocking arm but longer than the same, a link connecting said rocking arms the distance between the pivotal point of said link and the axis of said .rocking arm being the same at both arms, an oscillating auxiliary link pivoted to the extremity of said longer rocking arm, an arm projecting rearward from the crosshead of the engine to which the auxiliary link is pivoted, and a valve rod connected to the extremity of said rocking' arm at the saine pivotal point as said auxiliary link and attached at its other end to t-he auxiliary valve, the valve :rods ofthe main valves being pivcted to said auxiliary link at a point below its pivotal connection with said rocking arm.

7. In valve gears for engines, a cylinder, a steam chest, admission and exhaust ports connecting the steam chest with the cylinder, auxiliary exhaust ports, a main valve een trolling the admission and exhaust through the steam ports, a compression regulating valve controlling the auxiliary exhaust ports and mechanism for'movi'ng the mai valve at an accelerated speed and linear advance relative to the speed and linear advance of the auxiliary valve, said auxiliary valve having a valve face shorter than the valve face of said main valve.

In testimony whereof I have signed my name to this specification in the presence of Vtwo subscribing Witnesses.

CHA S F. PRESCQTT. Witnesses WARREN E. WILLIS, EUGENE V. GoGear. 

